Tension measuring apparatus

ABSTRACT

A tension measuring apparatus includes a displacement part that is displaced in accordance with tension or a change of the tension of a wire rod to be measured when the displacement part is caused to abut against the wire rod to receive the tension of the wire rod, an elastic body that is elastically deformed in accordance with displacement of the displacement part, and a heat flow sensor that detects a heat flow caused by elastic deformation of the elastic body.

This application claims priority to Japanese Patent Application No.2016-81188 filed on Apr. 14, 2016, the entire contents of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a tension measuring apparatus formeasuring the tension of a wire rod.

2. Description of Related Art

There is a demand for a technique for controlling the tension of a wirerod. For example, an automatic winding machine for winding a wire rod ona bobbin is required to maintain the tension of the wire rod constantfor the purpose of increasing the quality and working efficiency.

Japanese Patent Application Laid-open No. 64S-41207 discloses atechnique in which a tension control apparatus is used for controllingthe tension applied to a wire rod by this apparatus so that the tensionis maintained constant. More specifically, the tension control apparatusdescribed in this patent document includes an arm for supporting a wire,a tension roller for applying a tension to the wire rod, a rotationalresistance imparting mechanism for imparting a rotational resistance tothe tension roller and a controller for issuing commands to therotational resistance imparting mechanism. According to the techniquedisclosed in this patent document, the tension of a wire rod isgenerated by supporting the wire rod with the arm. Further, the tensionof the wire rod can be changed at any time by changing the rotationalresistance which the rotational resistance imparting mechanism appliesto the tension roller based on the command received from the controller.The command issued from the controller is set taking into account theaging variation of the tension of the wire rod while the automaticwinding machine is in operation.

That is, according to the technique disclosed in this patent document,the tension of a wire rod is controlled by supporting the wire rod withthe arm, and adjusting the rotational resistance imparted to the tensionroller by the rotational resistance imparting mechanism.

As explained above, the tension control apparatus described in the abovepatent document is configured to adjust the tension of a wire rod bycontrolling each of the support resistance of the arm and the rotationalresistance of the tension roller. This conventional tension controlapparatus has a problem that there may occur a control error due todeflection or vibration of the arm, or an error in controlling thetension roller by the rotational resistance imparting mechanism.Accordingly, this conventional tension control apparatus is not capableof controlling the tension of a wire rod with a sufficiently high degreeof accuracy. Under the circumstances, there is a strong demand for atechnique that enables accurately measuring tension of a wire rod.

It is known to use a load cell that converts a load into an electricsignal for measuring the tension of a wire as the load. Such a load cellis installed such that its sensing part including a sensor is in directcontact with a wire rod so that the sensing part directly receives thetension of the wire rod. Accordingly, there is a concern that the sensormay be damaged by the tension of the wire rod.

SUMMARY

An exemplary embodiment provides a tension measuring apparatusincluding:

-   -   a displacement part that is displaced in accordance with tension        or a change of the tension of a wire rod when the displacement        part is caused to abut against the wire rod to receive the        tension of the wire rod;    -   an elastic body that is elastically deformed in accordance with        displacement of the displacement part; and    -   a heat flow sensor that detects a heat flow caused by elastic        deformation of the elastic body.

According to the exemplary embodiment, there is provided a tensionmeasuring apparatus capable of directly measuring the tension of a wirerod, and whose sensor is not easily damaged.

Other advantages and features of the invention will become apparent fromthe following description including the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a diagram showing the overall structure of a tension measuringapparatus according to a first embodiment of the invention;

FIG. 2 is another diagram showing the overall structure of the tensionmeasuring apparatus according to the first embodiment of the invention;

FIG. 3 is a plan view of a heat flow sensor included in the tensionmeasuring apparatus according to the first embodiment of the invention;

FIG. 4 is a cross-sectional view of FIG. 3 taken along line IV-IV;

FIG. 5 is a diagram showing the overall structure of a tension measuringapparatus according to a second embodiment of the invention;

FIG. 6 is another diagram showing the overall structure of the tensionmeasuring apparatus according to the second embodiment of the invention;

FIG. 7 is a diagram showing the overall structure of a tension measuringapparatus according to a third embodiment of the invention;

FIG. 8 is another diagram showing the overall structure of the tensionmeasuring apparatus according to the third embodiment of the invention;

FIG. 9 is a diagram showing the overall structure of a tension measuringapparatus according to a fourth embodiment of the invention;

FIG. 10 is another diagram showing the overall structure of the tensionmeasuring apparatus according to the fourth embodiment of the invention;

FIG. 11 is a diagram showing the overall structure of a tensionmeasuring apparatus according to a variant embodiment of the invention;and

FIG. 12 is another diagram showing the overall structure of the tensionmeasuring apparatus according to the variant embodiment of theinvention.

PREFERRED EMBODIMENTS OF THE INVENTION First Embodiment

A tension measuring apparatus 1 according to a first embodiment of theinvention is described with reference to FIGS. 1 to 4. The tensionmeasuring apparatus 1 is used for measuring the tension of a wire rod100 which is fed to a bobbin to be wound thereon by an automatic windingmachine. FIG. 1 shows the overall structure of the tension measuringapparatus 1 at a point of time of starting a measurement. FIG. 2 isshows the overall structure of the tension measuring apparatus 1 at apoint of time when the tension of the wire rod 100 has increased afterstarting the measurement. The arrow Y1 in FIG. 1 shows the direction ofdeformation of an elastic body 3 when the tension of the wire rod 100has increased.

As shown in FIGS. 1 and 2, the tension measuring apparatus 1 includes adisplacement part 2, the elastic body 3, a heat flow sensor 4,plate-like members 5 and 6, a tension calculation part 7 and a displaypart 8. The plate-like member 6, the heat flow sensor 4, the elasticbody 3, the plate-like member 5 and the displacement part 2 are stackedin this order from the downward side as shown in FIGS. 1 and 2.

The displacement part 2 includes a portion which the wire rod 100 abutsagainst to receive the tension of the wire rod 100. The displacementpart 2 is displaced in accordance with the tension of the wire rod 100against which the portion of the displacement part 2 is caused to abut.As shown in FIGS. 1 and 2, the displacement part 2 includes a proximalportion 2 a and a roller portion 2 b.

The proximal portion 2 a of the displacement part 2 directly orindirectly connects with the elastic part 3 to apply a pressing force tothe elastic part 3 depending on the tension of the wire rod 100. In thisembodiment, as shown in FIGS. 1 and 2, the proximal portion 2 a of thedisplacement part 2 is formed in a roughly cubic shape, and connects tothe elastic body 3 through the plate-like member 5. The proximal portion2 a of the displacement part 2 is made of stainless steel, for example.The plate-like member 5 is made of stainless steel, for example.

The roller portion 2 b is a cylindrical rotating body rotatablysupported by the proximal portion 2 a. The roller portion 2 b rotateswhen it is caused to abut against the wire rod 100, to feed the wire rod100 in the feed direction shown by the arrow in FIGS. 1 and 2. Theroller portion 2 b is made of Delrin resin, for example.

The proximal portion 2 a and the roller portion 2 b are displaced inaccordance with the tension of the wire rod 100. Specifically, theproximal portion 2 a is displaced together with the roller portion 2 bin the direction perpendicular to the feed direction when the rollerportion 2 b receives the tension of the wire rod 100. As a result of thedisplacement of the proximal portion 2 a, the elastic body 3 is pressedby the plate-like member 5 and is deformed accordingly.

The elastic body 3 is deformed in accordance with the displacement ofthe displacement part 2 caused by the tension or a change of the tensionof the wire rod 100. The elastic body 3 is made of urethane rubber, forexample. The elastic modulus of the material of the elastic body 3 issmaller than that of the displacement part 2 in this embodiment.However, the elastic modulus of the material of the elastic body 3 maybe larger than that of the displacement part 2.

The heat flow sensor 4 is a sensor for detecting a heat flow caused byan elastic deformation of the elastic body 3. The heat flow sensor 4 isdisposed at a position where a heat flow caused by an elasticdeformation of the elastic body 3 can be detected. In this embodiment,the heat flow sensor 4 is disposed so as to be in contact with theelastic body 3. The heat flow sensor 4 outputs a sensor signal dependingon a heat flow directing from the inside to the outside of the elasticbody 3.

As shown in FIGS. 3 and 4, the heat flow sensor 4 has a structure inwhich an insulating substrate 40, a front surface protecting member 41and a back surface protecting member 42 are integrated such that firstinter-layer connecting members 43 and second inter-layer connectingmembers 44 are connected in series alternately therein. In FIG. 3, thefront surface protecting member 41 is omitted from illustration. Each ofthe insulating substrate 40, the front surface protecting member 41 andthe back surface protecting member 42 is made of resin material havingflexibility (thermoplastic resin, for example) formed in a film shape.The insulating substrate 40 is formed with first via holes 401 andsecond via holes 402 which penetrate through in the thickness direction.Each of the first via holes 401 is filled with a first inter-layerconnecting member 43 made of thermoelectric material (metal orsemiconductor, for example). Each of the second via holes 402 is filledwith a second inter-layer connecting member 44 made of thermoelectricmaterial (metal or semiconductor, for example), which is different fromthe first inter-layer connecting member 43. A front surface conductorpattern 411 is disposed on the front surface 40 a of the insulatingsubstrate 40. The front surface conductor pattern 411 makes a connectingpart that connects one end of the first inter-layer connecting member 43to one end of the second inter-layer connecting member 44. A backsurface conductor pattern 421 is disposed on the back surface 40 b ofthe insulating substrate 40. The back surface conductor pattern 421makes a connecting part that connects the other end of the firstinter-layer connecting member 43 to the other end of the secondinter-layer connecting member 44. In the following, the side on the oneend of the first or second inter-layer connecting member 43 or 44, thatis, the side on the front surface protecting member 41 is referred to asthe front side of the heat flow sensor 4. Likewise, the side on theother end of the first or second inter-layer connecting member 43 or 44,that is, the side on the back surface protecting member 42 is referredto as the back side of the heat flow sensor 4.

As shown in FIGS. 1 and 2, the heat flow sensor 4 having the abovedescribed structure is disposed such that the elastic body 3 is locatedon the front side of the heat flow sensor 4. The heat flow sensor 4 isfixed to the plate-like member 6 which is disposed on the back side ofthe heat flow sensor 4.

When a heat flow passes the heat flow sensor 4 in the thicknessdirection of the heat flow sensor 4, a difference in temperature occursbetween the front side and the back side of the heat flow sensor 4. Morespecifically, when a heat flow passes the heat flow sensor 4 in thethickness direction of the heat flow sensor 4, a difference intemperature occurs between the connecting parts on the side of the oneends of the first and second inter-layer connecting members 43 and 44and the connecting parts on the side of the other ends of the first andsecond inter-layer connecting members 43 and 44. As a result, anelectromotive force occurs in the first and second inter-layerconnecting members 43 and 44 due to the Seebeck effect. The heat flowsensor 4 outputs, as a sensor signal (a voltage signal, for example) theelectromotive force depending on the heat flow passing between the frontside and the back side of the heat flow sensor 4. In this embodiment,the heat flow sensor 4 is configured to generate a positiveelectromotive force when a heat flow passes from the front side to theback side of the heat flow sensor 4.

The elastic body 3 generates heat therein when the elastic body 3 iscompressed or expanded, and generates cold therein when the elastic body3 returns from a state of being applied with an external force fromoutside to be compressed to the initial state after the external forceis released. There is a correlation between the magnitude of theabsolute value of an electromotive force generated by the heat flowsensor 4 and a deformation of the elastic body 3 (the amount orvariation of a deformation of the elastic body 3, for example).Generally, as the deformation amount of the elastic body 3 increases, aheat flux caused by the deformation of the elastic body 3 increases andthe temperature difference between the front side and the back side ofthe heat flow sensor 4 increases. Accordingly, as the deformation amountof the elastic body 3 increases, the temperature difference between theconnecting parts on the side of the one ends of the first and secondinter-layer connecting members 43 and 44 and the connecting parts on theside of the other ends of the first and second inter-layer connectingmembers 43 and 44 increases, as result of which the absolute value ofthe electromotive force generated by the heat flow sensor 4 increases.

Since the heat flow sensor 4 has the above described structure, it canbe disposed on various surfaces which are not flat (curved surfaces, forexample). In addition, since the thickness of the heat flow sensor 4 canbe made small while ensuring a sufficiently large electromotive force tobe generated, it is possible to reduce a detection error by reducing thethermal resistance in the heat flow sensor 4 by reducing the thicknessof the heat flow sensor 4.

The tension calculation part 7 calculates the tension of change of thetension of the wire rod 100 based on a heat flow caused by an elasticdeformation of the elastic body 3, which is detected by the heat flowsensor 4. More specifically, the tension calculation part 7 calculatesthe tension or a change of the tension of the wire rod 100 based on thesensor signal outputted from the heat flow sensor 4, that is, anelectromotive force that has occurred in the heat flow sensor 4. Thetension calculation part 7 is an electronic control unit comprised of amicrocomputer, a memory as a storage device, and peripheral circuits.The memory stores data representing a relationship between the tensionof the wire rod 100 and the electromotive force to be generated by theheat flow sensor 4 when the plate-like member 6 is placed at apredetermined position. Further, the memory stores data representing arelationship between a change of the tension of the wire rod 100 and theelectromotive force to be generated by the heat flow sensor 4. Thememory is a non-transitory storage medium.

Also, the tension calculation part 7 controls the operation of thedisplay part 8 by performing a calculation process in accordance withprograms stored in the memory, so that the tension or a change of thetension of the wire rod 100 is displayed on the display part 8.

Next, the operation of the tension measuring apparatus 1 having theabove described structure is explained.

As shown in FIG. 1, the tension measuring apparatus 1 is placed at apredetermined position, and the rod wire 100 is caused to abut againstthe displacement part 2. At this time, the displacement part 2 displacesdepending on the position of the displacement part 2 and the tension ofthe wire rod 100, causing the elastic body 3 to be compressed to acertain extent.

When the elastic body 3 is compressed as above, the molecules inside theelastic body 3 are aligned as a result of which heat is generated insidethe elastic body 3. Accordingly, a heat flow from the inside of theelastic body 3 to the outside occurs. Since this heat flow passes thefront side of the heat flow sensor 4, there occurs a temperaturedifference between the front side and the back side of the heat flowsensor 4. As a result, an electromotive force occurs as the sensorsignal depending on the tension of the wire rod 100, and the tensioncalculation part 7 calculates the tension of the wire rod 100 based onthe sensor signal. Specifically, to calculate the tension of the wirerod 100, the tension calculation part 7 reads the data representing therelationship between the tension of the wire rod 100 and theelectromotive force generated by the heat flow sensor 4 from the memory.The tension of the wire rod 100 calculated by the tension calculationpart 7 at this time is stored in the memory as an initial tension at thetime of start of measurement. Incidentally, the heat flux caused bycompressing the elastic body 3 at the time of start of measurement isreleased to the outside with the passage of time, and becomesundetectable after an elapse of a predetermined time.

In a case where the tension of the wire rod 100 increases after thestart of measurement, the displacement part 2 is displaced downward inFIG. 2, and as a result the elastic body 3 is compressed more then thanat the start of measurement. In this case, an electromotive force occursdepending on the degree of change of the tension of the wire rod 100.The tension calculation part 7 calculates the tension of the wire rod100 at this moment that has increased from the initial tension as asecond stage tension. If the tension of the wire rod 100 increasesbeyond a predetermined value, the wire rod 100 becomes roughly linear inshape.

In a case where the tension of the wire rod 100 decreases after thestart of measurement or after being compressed more after the start ofmeasurement, the displacement part 2 is displaced upward in FIG. 2 toreturn to the initial state. In this case, the compression of theelastic body 3 is released and the elastic body 3 restores from theelastic deformation, as a result of which cold occurs inside the elasticbody 3. As a result, since the temperature of the front side of the heatflow sensor 4 decreases, the temperature difference between the frontside and the back side of the heat flow sensor 4 is changed from thatbefore the decrease of the tension of the wire rod 100. Accordingly,there occurs a change in the electromotive force generated by the heatflow sensor 4. The tension calculation part 7 calculates the tension ofthe wire rod 100 at this moment that has decreased from the initialtension or the second stage tension. The electromotive force generatedby the heat flow sensor 4 at this moment is lower than that before thetension of the wire rod 100 decreases. When the sign of the temperaturedifference between the front side and the back side of the heat flowsensor 4 changes after the tension of the wire rod 100 decreases, alsothe sign of the electromotive force changes. The tension calculationpart 7 causes the display part 8 to display change of the tension of thewire rod 100.

According to the tension measuring apparatus 1, the displacement part 2is in accordance with the tension or a change of the tension of the wirerod 100, and the elastic body 3 is deformed in accordance with thedisplacement of the displacement part 2. The tension measuring apparatus1 is capable of detecting a change of the heat flow due to deformationof the elastic body 3 by the heat flow sensor 4 to measure the tensionand a change of the tension of the wire rod 100. The tension measuringapparatus 1 is configured such that the tension of the wire rod 100 isnot directly received by the heat flow sensor 4, but the elastic body 3is caused to abut against the heat flow sensor 4. Therefore, accordingto the tension measuring apparatus 1, it is possible to prevent theproblem in the conventional art which uses a load cell that a sensor maybe easily damaged.

Incidentally, according to the tension measuring apparatus 1, thetension or a change of the tension of the wire rod 100 can be measuredeven while the automatic winding machine is in operation to feed thewire rod 100. Further, according to the tension measuring apparatus 1,the tension or a change of the tension of the wire rod 100 can bemeasured even while the automatic winding machine is out of operation,and the wire rod 100 is stationary. As described above, the tensionmeasuring apparatus 1 includes the displacement part 2 which isdisplaced in accordance with the tension or a change of the tension ofthe wire rod 100 when it is caused to abut against the wire rod 100 toreceive the tension of the wire rod 100, the elastic body 3 which iselastically deformed in accordance with the displacement of thedisplacement part 2, and the heat flow sensor 4 which detects a heatflow caused by the elastic deformation of the elastic body 3.

In the tension measuring apparatus 1, the displacement part 2 isdisplaced in accordance with the tension or a change of the tension ofthe wire rod 100, and the elastic body 3 is deformed in accordance withthe deformation of the displacement part 2. According to the tensionmeasuring apparatus 1, it is possible to detect a change of a heat flowcaused by a deformation of the elastic body 3 to measure the tension ora change of the tension of the wire rod 100. As described above, thetension measuring apparatus 1 is configured such that the tension of thewire rod 100 is not directly received by the heat flow sensor 4, but theelastic body 3 is caused to abut against the heat flow sensor 4.Therefore, according to the tension measuring apparatus 1, it ispossible to prevent the problem in the conventional art which uses aload cell that a sensor may be easily damaged.

In the tension measuring apparatus 1, the displacement part 2 includesthe roller portion 2 b which rotates when caused to abut against thewire rod 100 to feed the wire rod 100.

Accordingly, the tension measuring apparatus 1 can displace thedisplacement part 2 to measure the tension of the wire rod 1200 whilefeeding the wire rod 100 smoothly using the roller portion 2 b.

Second Embodiment

Next a second embodiment of the invention is described with a focus ondifferences with the first embodiment referring to FIGS. 5 and 6.

In FIGS. 5 and 6, the tension calculation part 7 and the display part 8are omitted from illustration. In FIG. 5, the arrow Y2 shows thedirection of displacement of the displacement part 2 at a time when thetension of the wire rod 100 has changed, and the arrow Y3 shows thedirection of displacement of the elastic body 3 at a time when thetension of the wire rod 100 has increased.

As shown in FIGS. 5 and 6, the tension measuring apparatus 1 accordingto the second embodiment includes, in addition to the displacement part2, the elastic body 3, the heat flow sensor 4 and the display part 8, acase part 9 housing the elastic body 3, a support mechanism 10 forcausing the case part 9 to support the displacement part 2, a radiator11, and a plate-like member 12.

In this embodiment, the displacement part 2 rotates with the supportmechanism 10 as a fulcrum in accordance with the tension or a change ofthe tension of the wire rod 100 at a time when the displacement part 2is caused to abut against the wire rod 100. As shown in FIGS. 5 and 6,the displacement part 2 includes a proximal portion 2 c having a rodshape and a roller portion 2 d.

The roller portion 2 d is formed in a distal end of the proximal portion2 c. The proximal portion 2 c is made of stainless steel, for example.The roller portion 2 d is made of Delrin resin, for example.

The roller portion 2 d is a cylindrical rotating body supported by thecase part 9 so as to be rotatable independently of the whole rotation ofthe displacement part 2 to feed the wire rod 100. As shown in FIGS. 5and 6, the roller portion 2 d rotates when it is caused to abut againstthe wire rod 100, and as a result it feeds the wire rod 100 abuttingagainst the roller portion 2 d in the feed direction of the arrow inFIG. 6.

In this embodiment, the elastic body 3 is disposed on one surface of theplate-like member 12, which faces the displacement part 2. The elasticbody 3 is disposed so as to be abutted against the proximal portion 2 cof the displacement part 2.

The heat flow sensor 4 is disposed on the other surface of theplate-like member 12, which does not face the displacement part 2.

The support mechanism 10 is a mechanism for enabling the case part 9 torotatably support the displacement part 2. The support mechanism 10includes a rotation shaft which makes an axis of rotation of thedisplacement part 2. This rotation shaft is inserted in a through holeformed in the proximal portion 2 c of the displacement part 2. In thetension measuring apparatus 1 of this embodiment, the distance betweenthe support mechanism 10 and the roller portion 2 d is longer than thedistance between the support mechanism 10 and a portion of the proximalportion 2 c at which the displacement part 2 is caused to abut againstthe elastic body 3. That is, in this embodiment, the support mechanism10 makes a fulcrum, the portion of the proximal portion 2 c which abutsagainst the elastic body 3 makes a point of action, and the rollerportion 2 d makes a point of effort, so that the elastic body 3 isdeformed using the principle of leverage.

The radiator 11 is comprised of a heat dissipation fin having a largeheat dissipation area for dissipating the heat of the inside of the heatflow sensor 4 and its vicinity to the outside. As shown in FIGS. 5 and6, the radiator 11 is disposed on the side opposite the elastic body 3with the heat sensor 4 between them.

The plate-like member 12 is supported by the case part 9, and supportsthe elastic body 3 at one surface thereof. The heat flow sensor 4 andthe radiator 11 are fixed to the other surface of the plate-like member12. The plate-like member 12 is made of stainless steel, for example.The plate-like member 12 functions as an intervening part for preventinga force caused by an elastic deformation of the elastic body 3 inaccordance with the tension of the wire rod 100 from affecting the heatflow sensor 4. In this embodiment, since the plate-like member 12 isprovided as an intervening part, the heat flow sensor 4 can be preventedfrom being damaged.

In the tension measuring apparatus 1 according to the second embodiment,the displacement part 2 is deformed in accordance with the tension or achange of the tension of the wire rod 100 as in the case of the firstembodiment. Therefore, also according to the second embodiment, sincethe elastic body 3 is deformed in accordance with displacement of thedisplacement part 2, the tension or a change of the tension of the wirerod 100 can be measured by detecting a change of a heat flow caused bythe deformation of the elastic body.

Next, the operation of the tension measuring apparatus 1 according tothe second embodiment is explained.

As shown in FIG. 5, the tension measuring apparatus 1 is placed at apredetermined position, and the rod wire 100 is caused to abut againstthe displacement part 2. At this time, the displacement part 2 rotateswith the support mechanism 10 as a fulcrum in accordance with theposition of the displacement part 2 and the tension or a change of thetension of the wire rod 100, causing the elastic body 3 to be compressedto some extent.

When the elastic body 3 is compressed as above, the molecules inside theelastic body 3 are aligned, as a result of which heat is generatedinside the elastic body 3. Accordingly, a heat flow from the inside ofthe elastic body 3 to the outside occurs. Since this heat flow passesthe front side of the heat flow sensor 4, there occurs a temperaturedifference between the front side and the back side of the heat flowsensor 4. As a result, an electromotive force occurs as the sensorsignal corresponding to the tension of the wire rod 100, and the tensioncalculation part 7 calculates the tension of the wire rod 100 based onthe sensor signal.

In a case where the tension of the wire rod 100 increases after thestart of measurement, the displacement part 2 rotates downward with thesupport mechanism 10 as a fulcrum downward in FIG. 6, and as a result,the elastic body 3 is compressed more then than at the start ofmeasurement. In this case, an electromotive force in accordance with thedegree of a change of the tension of the wire rod 100 occurs. Thetension calculation part 7 calculates the tension of the wire rod 100 atthis moment that has increased. If the tension of the wire rod 100increases beyond a predetermined value, the wire rod 100 becomes roughlylinear in shape.

In a case where the tension of the wire rod 100 decreases after thestart of measurement or after being compressed more after the start ofmeasurement, the displacement part 2 rotates upward in FIG. 6 with thesupport mechanism 10 as a fulcrum. In this case, the compression of theelastic body 3 is released and the elastic body 3 restores from theelastic deformation, as a result of which cold occurs inside the elasticbody 3. As a result, since the temperature of the front side of the heatflow sensor 4 decreases, the temperature difference between the frontside and the back side of the heat flow sensor 4 is changed from thatbefore the decrease of the tension of the wire rod 100. Accordingly,there occurs a change in the electromotive force generated by the featflow sensor 4. The tension calculation part 7 calculates the tension ofthe wire rod 100 at this moment that has decreased. The electromotiveforce generated by the heat flow sensor 4 at this moment is lower thanthat before the tension of the wire rod 4 decreases. When the sign ofthe temperature difference between the front side and the back side ofthe heat flow sensor 4 changes after the tension of the wire rod 100decreases, also the sign of the electromotive force changes.

As described above, according to the tension measuring apparatus 1 ofthis embodiment, both the tension and a change of the tension can bemeasured like the first embodiment.

In addition, in the tension measuring apparatus 1 of this embodiment,the tension of the wire rod 100 is not directly received by the heatflow sensor 4, but the elastic body 3 is abutted against the heat flowsensor 4 and the plate-like member 12 is intervened between thedisplacement part 2 and the heat flow sensor 4. Accordingly, the heatflow sensor 4 is not easily damaged.

Further, in the tension measuring apparatus 1 of this embodiment, thedisplacement part 2 is caused to rotate by the tension of the wire rod100, and the elastic body 3 is deformed by the rotation of thedisplacement part 2. That is, in the tension measuring apparatus 1 ofthis embodiment, the tension of the wire rod 100 is converted to a largeforce using the principle of leverage. Therefore, since the position ofthe point of effort (that is, the part of the proximal portion of thedisplacement part 2 which is caused to abut against the elastic body 3)to the fulcrum (that is, the support mechanism 10) and the point ofeffort (that is, the roller portion 2 d) can be adjusted, therelationship between the tension of the wire rod 100 and thedisplacement of the elastic body 3 or the relationship between thetension of the wire rod 100 and the electromotive force of the heat flowsensor 4 can be set in a wide range. For example, it is possible toaccommodate such a case where the elastic body 3 should be deformedgreatly even when the tension of the wire rod 100 is small by increasingthe distance between the fulcrum (that is, the supporting mechanism 10)of the displacement part 2 and the point of effort (that is, the rollerportion 2 d).

Third Embodiment

Next a third embodiment of the invention is described with a focus ondifferences with the first embodiment referring to FIGS. 7 and 8.

In FIGS. 7 and 8, the tension calculation part 7 and the display part 8are omitted from illustration. In FIG. 7, the arrow Y4 shows thedirection of displacement of the displacement part 2 at a time when thetension of the wire rod 100 has changed, and the arrows Y5 to Y8 showthe directions of displacement of the elastic body 3 at a time when thetension of the wire rod 100 has increased.

In this embodiment, the displacement part 2 includes the proximalportion 2 c and a roller portion 2 d. As shown in FIGS. 7 and 8, theproximal portion 2 c of the displacement part 2 includes a rod-shapedportion 2 ca formed with the roller portion 2 d at its one distal endand formed with a polyhedral portion 2 cb at its other distal end. Inthis embodiment, the polyhedral portion 2 cb of the displacement part 2has a cubic shape. The rod-shaped portion 2 ca and the polyhedralportion 2 cb of the displacement part 2 rotate together with the supportmechanism 10 as a fulcrum. The rod-shaped portion 2 ca of thedisplacement part 2 is made of stainless steel, for example. The rollerportion 2 d is made of Delrin resin, for example. The polyhedral portion2 cb of the displacement part 2 is made of stainless steel, for example.

As shown in FIGS. 7 and 8, the elastic body 3 is disposed at a pluralityof positions around the polyhedral portion 2 cb in this embodiment. Eachof the plurality of the elastic bodies 3 faces an opposite one of aplurality of the surfaces of the polyhedral portion 2 cb. That is, theelastic bodies 3 are disposed such that each one of them abuts acorresponding one of the surfaces of the polyhedral portion 2 cb and isdeformed when the polyhedral portion 2 cb rotates. In this embodiment,the elastic bodies 3 are four spherical elastic bodies. When thepolyhedral portion 2 cb of the displacement part 2 rotates with thesupport mechanism 10 as a fulcrum, the four spherical elastic bodies arecompressed by the displacement of the surfaces of the polyhedral portion2 cb due to the rotation.

In the third embodiment, the plate-like member 12 is removed. The casepart 9 functions as the intervening part that prevents a force caused byan elastic deformation of the elastic body due to the tension of thewire rod 100 from affecting the heat flow sensor 4.

Next, the operation of the tension measuring apparatus 1 according tothe third embodiment is explained.

As shown in FIGS. 7 and 8, the tension measuring apparatus 1 is placedat a predetermined position, and the wire rod 100 is caused to abutagainst the displacement part 2. At this time, the displacement part 2is in a state of being caused to abut against the elastic body 3 so asto slightly compress the elastic body 3.

In this state, since the elastic body 3 is only slightly compressed, theelectromotive force generated in the heat flow sensor 4 at this moment(that is, at the start of measurement) is approximately zero.

In a case where the tension of the wire rod 100 increases thereafter,the displacement part 2 rotates in the direction A or B with the supportmechanism 10 as a fulcrum. Here, it is assumed that the displacementpart 2 rotates in the direction A. The elastic body 3 is compressed morethen than at the start of measurement. In this case, there occurs anelectromotive force in accordance with the degree of a change of thetension of the wire rod. The tension calculation part 7 calculates thetension of the wire rod 100 at this moment that has increased. If thetension of the wire rod 100 increases beyond a predetermined value, thewire rod 100 becomes roughly linear in shape.

In a case where the tension of the wire rod 100 decreases after thestart of measurement or after being compressed more after the start ofmeasurement, the displacement part 2 rotates in the direction B in FIG.7 with the support mechanism 10 as a fulcrum. In this case, thecompression of the elastic body 3 is released and the elastic body 3restores from the elastic deformation, as a result of which cold occursinside the elastic body 3. As a result, since the temperature of thefront side of the heat flow sensor 4 decreases, the temperaturedifference between the front side and the back side of the heat flowsensor 4 is changed from that before the decrease of the tension of thewire rod 100. Accordingly, there occurs a change in the electromotiveforce generated by the feat flow sensor 4. The tension calculation part7 calculates the tension of the wire rod 100 at this moment that hasdecreased. The electromotive force generated by the heat flow sensor 4at this moment is lower than that before the tension of the wire rod 4decreases. When the sign of the temperature difference between the frontside and the back side of the heat flow sensor 4 changes after thetension of the wire rod 100 decreases, also the sign of theelectromotive force changes.

As described above, according to the tension measuring apparatus 1 ofthis embodiment, both the tension and a change of the tension of thewire rod 100 can be measured like the first embodiment.

In this embodiment, the heat flow sensor 4 can be prevented from beingdamaged, like in the fourth embodiment.

Therefore, the relationship between the tension of the wire rod 100 andthe displacement of the elastic body 3 or the relationship between thetension of the wire rod 100 and the electromotive force of the heat flowsensor 4 can be set in a wide range.

Further, since the elastic bodies 3 can be deformed efficiently usingthe respective surfaces of the polyhedral portion 2 cb, it is possibleto increase the electromotive force of the heat flow rate sensor 4efficiently.

Fourth Embodiment

Next a fourth embodiment of the invention is described with a focus ondifferences with the first embodiment referring to FIGS. 9 and 10.

In FIGS. 9 and 10, the tension calculation part 7 and the display part 8are omitted from illustration. In FIG. 9, the arrow Y9 shows thedirection of displacement of the displacement part 2 at a time when thetension of the wire rod 100 has changed, the arrow Y10 shows thedirection of displacement of the elastic body 3 at a time when thetension of the wire rod 100 has increased causing the displacement part2 to displace in the direction shown by the arrow D, and the arrow Y11shows the direction of displacement of the elastic body 3 at a time whenthe tension of the wire rod 100 has increased causing the displacementpart 2 to displace in the direction shown by the arrow C.

As shown in FIGS. 9 and 10, the elastic body 3 includes a first part 3 aand a second part 3 b. The first part 3 a is disposed on the side of onedirection (direction C) of the rotation of the displacement part 2. Thesecond part 3 a is disposed on the side of the other direction(direction D) of the rotation of the displacement part 2.

As shown in FIGS. 9 and 10, in this embodiment, the plate-like member 12is absent, and instead, plate-like members 13 and 14 are provided. Theplate-like members 13 and 14 are fixed to the case part 9.

The first part 3 a of the elastic body 3 is disposed between theplate-like member 13 and the proximal portion 2 c of the displacementpart 2 so as to be compressed therebetween. The second part 3 b of theelastic body 3 is disposed between the plate-like member 14 and theproximal portion 2 c of the displacement part 2 so as to be compressedtherebetween.

In this embodiment, the heat flow sensor 4 is comprised of a firstdetection part 4 a for detecting mainly a heat flow caused by an elasticdeformation of the first part 3 a of the elastic body 3, and a seconddetection part 4 b for detecting mainly a heat flow caused by an elasticdeformation of the second part 3 b of the elastic body 3. Each of thefirst and second detection parts 4 a and 4 b is the same in structure asthe heat flow sensor 4 described in the first embodiment. The firstdetection part 4 a is configured to generate a positive electromotiveforce when a heat flow passes from the front side to the back side ofthe first detection part 4 a. The second detection part 4 b isconfigured to generate a positive electromotive force when a heat flowpasses from the front side to the back side of the second detection part4 b.

As shown in FIGS. 9 and 10, the first detection part 4 a of the heatflow sensor 4 is disposed opposite to the elastic body 3 across theplate-like member 13. Likewise, the second detection part 4 b of theheat flow sensor 4 is disposed opposite to the elastic body 3 across theplate-like member 14. The first and second detection parts 4 a and 4 bof the heat flow sensor 4 are electrically connected to the tensioncalculation part 7. The first detection part 4 a generates anelectromotive force in accordance with a deformation amount of the firstpart 3 a of the elastic body 3 when a heat flow has occurred in thefirst part 3 a of the elastic body 3. The second detection part 4 bgenerates an electromotive force in accordance with a deformation amountof the second part 3 b of the elastic body 3 when a heat flow hasoccurred in the second part 3 b of the elastic body 3.

The plate-like member 13 functions as an intervening part that preventsa force caused by an elastic deformation of the first part 3 a of theelastic body 3 due to the tension of the wire rod 100 from affecting thefirst detection part 4 a of the heat flow sensor 4. The plate-likemember 14 functions as an intervening part that prevents a force causedby an elastic deformation of the second part 3 a of the elastic body 3due to the tension of the wire rod 100 from affecting the seconddetection part 4 b of the heat flow sensor 4. The provision of theplate-like members 13 and 14 provides an advantage that the heat flowsensor 4 is not easily damaged.

In this embodiment, the tension calculation part 7 calculates thetension or a change of the tension of the wire rod 100 based on theelectromotive force detected by the first detection part 4 a and theelectromotive force detected by the second detection part 4 b of theheat flow sensor 4. More specifically, the tension calculation part 7calculates the tension or a change of the tension of the wire rod 100based on the difference between the electromotive force detected by thefirst detection part 4 a and the electromotive force detected by thesecond detection part 4 b of the heat flow sensor 4.

Next, the operation of the tension measuring apparatus 1 according tothe fourth embodiment is explained.

As shown in FIGS. 9 and 10, the tension measuring apparatus 1 is placedat a predetermined position, and the wire rod 100 is caused to abutagainst the displacement part 2. At this time, the tension measuringapparatus 1 is in a state of starting measurement where the displacementpart 2 of the tension measuring apparatus 1 compresses the first part 3a and the second part 3 b to some extent while it is caused to abutagainst the elastic body 3.

In this embodiment, the tension measuring apparatus 1 is left in thismeasurement starting state for a predetermined time so that the heatgenerated inside the elastic body 3 due to the compression of theelastic body is sufficiently dissipated to the outside. Accordingly, inthis state, the electromotive force of the heat flow sensor 4 becomesapproximately zero.

In a case where the tension of the wire rod 100 increases thereafter,the displacement part 2 rotates in the direction C or D shown in FIG. 9with the support mechanism 10 as a fulcrum as shown in FIG. 10. Here, itis assumed that the displacement part 2 rotates in the direction C. Thesecond part 3 b of the elastic body 3 is compressed in this state thanin the measurement starting state, while the first part 3 a of theelastic body 3 is released from the compression to restore from beingdeformed. As a result, heat occurs in the second part 3 b of the elasticbody 3, while cold occurs in the first part 3 a of the elastic body 3.Accordingly, a positive electromotive force occurs in the firstdetection part 4 a of the heat flow sensor 4, while a negativeelectromotive force occurs in the second detection part 4 b of the heatflow sensor 4. The tension calculation part 7 calculates a change of thetension of the wire rod 100 based on the difference between theelectromotive force that has occurred in the first detection part 4 band the electromotive force that has occurred in the second detectionpart 4 b. The value of a change of the tension of the wire rod 100calculated by the tension calculation part 7 at this time is larger thanthat calculated at the time of start of measurement. When heat due tocompression remains in the elastic body 3 or when the elastic body 3 hasheat due to circumferential heat, a positive electromotive force mayoccur also in the second detection part 4 b of the heat flow sensor 4.

According to this embodiment, since the tension or a change of thetension of the wire rod 100 is calculated based on the difference of theelectromotive forces of the two heat flow sensors (the first and seconddetection parts 4 a and 4 b), an advantage that the output of thetension calculation part 7 can be increased is obtained.

In a case where the tension of the wire rod 100 decreases after thestart of measurement, the displacement part 2 rotates in the direction Cor D in FIG. 9 with the support mechanism 10 as a fulcrum. Here, it isassumed that the displacement part 2 rotates in the direction D. In thiscase, the second part 3 b of the elastic body 3 is released from thecompression to restore from being deformed. Therefore, since cold occursinside the second part 3 b of the elastic body 3, the electromotiveforce occurring in the second detection part 4 b of the heat flow sensor4 decreases. On the other hand, since the first part 3 a of the elasticbody 3 is compressed, heat occurs inside the first part 3 a of theelastic body 3. As a result, the difference in electromotive forcebetween the first detection part 4 a and the second detection part 4 bdecreases, typically to a negative value. Accordingly, it is detected asa decrease of the tension of a belt 100 by an abnormality estimationpart 7.

According to the tension measuring apparatus 1 according to thisembodiment, both the tension and a change of the tension can bemeasured.

According to the tension measuring apparatus 1 according to thisembodiment, since the plate-like member 14 is provided, the heat flowsensor 4 is not easily damaged, like the second embodiment.

The tension measuring apparatus 1 according to this embodiment providesthe advantage that the relationship between the tension of the wire rod100 and the displacement of the elastic body 3 or the relationshipbetween the tension of the wire rod 100 and the electromotive force ofthe heat flow sensor 4 can be set in a wide range like the secondembodiment.

According to the tension measuring apparatus 1 according to thisembodiment, since the tension or a change of the tension of the wire rod100 is calculated based on the difference between the electromotiveforces of the two heat flow sensors (the first and second detectionparts 4 a and 4 b), the output of the tension calculation part 7 can beincreased. The output of the tension calculation part 7 in thisembodiment is approximately twice as that in the case of using a singleheat flow sensor.

Further, according to this embodiment, since the tension or a change ofthe tension is calculated based on the difference between twoelectromotive forces of the two heat sensors (the first and seconddetection parts 4 a and 4 b), and accordingly, temperature driftsincluded in the two electromotive forces cancel each other, it ispossible to prevent the temperature drifts from affecting the output ofthe tension calculation part 7. That is, in the case where only thesingle heat flow sensor 4 is provided, it is not possible to determine,when the electromotive force of the heat flow sensor 4 has increased,whether it is due to an increase of the tension of the wire rod 100causing the elastic body 3 to be deformed, or it is due to an increaseof the circumferential temperature. On the other hand, in the case wheretwo heat flow sensors (the first and second detection parts 4 a and 4 b)are provided, since the tension or a change of the tension of the wirerod 100 is calculated based on the difference between the twoelectromotive forces of the two heat flow sensors, it is possible todetermine that the elastic body 3 has been deformed due to an increaseof the tension of the wire rod 100 removing the effect of a change ofthe circumferential temperature. Specifically, in this embodiment, theheat flow sensor 4 is configured to generate a positive electromotiveforce when a heat flow passes from the front side to the back sidethereof, and the tension or a change of the tension of the wire rod 100is calculated based on the difference in electromotive force between thefirst and second detection parts 4 a and 4 b as two heat flow sensors.Accordingly, it is possible to remove the temperature drift caused by aheat flow passing from the back side to the front side of each of thefirst detection part 4 a and the second detection part 4 b, and removethe temperature drift caused by a heat flow passing from the front sideto the back side of each of the first detection part 4 a and the seconddetection part 4 b. Incidentally, the effect of the temperature driftcaused by a heat flow passing from the back side to the front side ofthe first detection part 4 a and a heat flow passing from the back sideto the front side of the second detection part 4 b can be removed bycalculating the tension or a change of the tension of the wire rod 100based on the sum of the electromotive forces of the two heat flowsensors (the first and second detection parts 4 a and 4 b), or bycausing the second detection part 4 b to generate a positiveelectromotive force when a heat flow passes from the front side to theback side of the second detection part 4 b.

Other Embodiments

It is a matter of course that various modifications can be made to theabove described embodiments as described below.

In the first to fourth embodiments, the displacement part 2 includes theroller portion 2 b or 2 d to feed the wire rod 100. However, the rollerportion 2 b or 2 d may not be provided if the wire rod 100 is fed bycausing the wire rod 100 to abut against the displacement part 2. Thatis, as shown in FIGS. 11 and 12, the wire rod 100 may be fed by causingthe wire rod 100 to abut against a surface 2 e of the displacement part2. In this case, it is preferable that the coefficient of friction ofthe surface 2 e is small so that the wire rod 100 abutting against thesurface 2 e can easily slide thereon. The tension calculation part 7 andthe display part 8 are omitted from illustration in FIGS. 11 and 12. Thearrow Y15 in FIG. 11 shows the direction of displacement of the elasticbody 3 at a time when the tension of the wire rod 100 has increased.

The above explained preferred embodiments are exemplary of the inventionof the present application which is described solely by the claimsappended below. It should be understood that modifications of thepreferred embodiments may be made as would occur to one of skill in theart.

What is claimed is:
 1. A tension measuring apparatus comprising: adisplacement part that is displaced in accordance with tension or achange of the tension of a wire rod when the displacement part is causedto abut against the wire rod to receive the tension of the wire rod; anelastic body that is elastically deformed in accordance withdisplacement of the displacement part; and a heat flow sensor thatdetects a heat flow caused by elastic deformation of the elastic body.2. The tension measuring apparatus according to claim 1, furthercomprising a case part for supporting the elastic body and a supportmechanism that causes the case part to rotatably support thedisplacement part, wherein the displacement part rotates with thesupport mechanism as a fulcrum, and the elastic body is elasticallydeformed in accordance with the displacement of the displacement partdue to rotation of the displacement part.
 3. The tension measuringapparatus according to claim 2, further comprising a tension calculationpart that calculates the tension of the wire rod based on the heat flowdetected by the heat flow sensor, wherein the elastic body includes afirst part and a second part, the displacement part compresses thesecond part and restores the first part when the displacement partrotates in a first rotational direction, and restores the second partand compresses the first part when the displacement part rotates in asecond rotational opposite to the first rotational direction, the heatflow sensor includes a first detection part for detecting a heat flowcaused by elastic deformation of the first part to generate anelectromotive force corresponding thereto and a second detection partfor detecting a heat flow caused by elastic deformation of the secondpart to generate an electromotive force corresponding thereto, and thetension calculation part calculates the tension of the wire rod based onan electromotive force generated by the first detection part and anelectromotive force generated by the second detection part.
 4. Thetension measuring apparatus according to claim 2, wherein thedisplacement part rotates when caused to abut against the wire rod tofeed the wire rod.
 5. The tension measuring apparatus according to claim1, further comprising an intervening part that intervenes between thedisplacement part and the heat flow sensor to prevent a force caused bythe elastic deformation of the elastic body from affecting the heat flowsensor.